Ch 1 Distributed systems EXAM Questions and Answers 2024/2025 | verified
What is a distributed system? - it is a collection of autonomous computing elements (either
hardware devices or software processes) that appear to the user as a single coherent system
Overlay network - - used to organize a collection of nodes
- in this case a node is a software process with a list of other processes it can send messages to
What are some things that makes coordination between nodes challenging? - - computing
elements are autonomous and need to coordinate
- no global clock
- authenticating a node to identify group membership can create scalability bottlenecks
What are the two ways to organize the collection of nodes for identifying which nodes can communicate
with one another? - 1. Overlay network, where the node has a list of other processes it can send
messages to
2. A node may need to first look up a neighbor
distribution transparency - the internal details of the distribution are hidden from the user, this
includes where the data is stored, on which computer a process is executing, or how the data is
replicated.
What challenge occurs when trying to create a single coherent system for a distributed environment and
distribution transparency? - - partial failures are inevitable and if the user is not aware of which
node is failing or the process that is failing on some set of unknown nodes then it will be hard to debug
- with distribution transparency there is a performance price (say an application repeatedly tries to
contact a server before giving up, masking the server failure before trying another one will slow down
the system)
-there is also a trade-off with geographic scalability, since hiding latencies and bandwidth restrictions are
difficult
- in some situations hiding distribution is not useful, like location based services on mobile phones where
you want to find the nearest store
, Middleware for distributed systems offer what? - - it is a manager of resources that extends over
multiple machines offering each application the same interface
- it is a software layer placed between the OS and the distributed applications
it also offers:
- facilities for interapplication communication
- security services
- accounting services
- masking of and recovery from failures
- the main difference with the OS is that middleware is offered in a networked env
What is a common communication service offered by middleware? - Remote Procedure Calls,
which allow an application to invoke a function that is implemented and executed on a remote computer
as if it was locally available
4 Design goals of Distributed Systems - - make resources easily accessible and shareable
- hide that resources are distributed
- open
- scalable
Uniform Resource Locator (URL) - - an address used for locating a document on the Web.
- it gives no clue as to the location of the websites main web server
Mobile phone users can continue a conversation while they move, this is an example of
________________________ - migration transparency
To hide replication it is necessary that all replicas _____________ - - have the same name
- so the system also needs to support location transparency, otherwise it is impossible to refer to replicas
in diff locations
What is a distributed system? - it is a collection of autonomous computing elements (either
hardware devices or software processes) that appear to the user as a single coherent system
Overlay network - - used to organize a collection of nodes
- in this case a node is a software process with a list of other processes it can send messages to
What are some things that makes coordination between nodes challenging? - - computing
elements are autonomous and need to coordinate
- no global clock
- authenticating a node to identify group membership can create scalability bottlenecks
What are the two ways to organize the collection of nodes for identifying which nodes can communicate
with one another? - 1. Overlay network, where the node has a list of other processes it can send
messages to
2. A node may need to first look up a neighbor
distribution transparency - the internal details of the distribution are hidden from the user, this
includes where the data is stored, on which computer a process is executing, or how the data is
replicated.
What challenge occurs when trying to create a single coherent system for a distributed environment and
distribution transparency? - - partial failures are inevitable and if the user is not aware of which
node is failing or the process that is failing on some set of unknown nodes then it will be hard to debug
- with distribution transparency there is a performance price (say an application repeatedly tries to
contact a server before giving up, masking the server failure before trying another one will slow down
the system)
-there is also a trade-off with geographic scalability, since hiding latencies and bandwidth restrictions are
difficult
- in some situations hiding distribution is not useful, like location based services on mobile phones where
you want to find the nearest store
, Middleware for distributed systems offer what? - - it is a manager of resources that extends over
multiple machines offering each application the same interface
- it is a software layer placed between the OS and the distributed applications
it also offers:
- facilities for interapplication communication
- security services
- accounting services
- masking of and recovery from failures
- the main difference with the OS is that middleware is offered in a networked env
What is a common communication service offered by middleware? - Remote Procedure Calls,
which allow an application to invoke a function that is implemented and executed on a remote computer
as if it was locally available
4 Design goals of Distributed Systems - - make resources easily accessible and shareable
- hide that resources are distributed
- open
- scalable
Uniform Resource Locator (URL) - - an address used for locating a document on the Web.
- it gives no clue as to the location of the websites main web server
Mobile phone users can continue a conversation while they move, this is an example of
________________________ - migration transparency
To hide replication it is necessary that all replicas _____________ - - have the same name
- so the system also needs to support location transparency, otherwise it is impossible to refer to replicas
in diff locations
